Means for sealing conductor end structures



March 2 5, 1952 J DIXON 2,590,160

MEANS FOR SEALING CONDUCTOR END STRUCTURES Filed June '7, 1950 F/G. f H 9 Inqenior Hep/"y Johnson 0/Xo/7 A itorneys Patented Mar. 25, 1952 MEANS FOR SEALING CONDUCTOR END STRUCTURES Henry Johnson Dixon, West Kirby, England, as-

signor to British Limited, London,

In Great Britain 1 Claim.

This invention relates to electrical apparatus of the kind in which a conducting member is supported within a metal casing by insulating material which is injected into the casing under pressure in a molten or plastic (hereinafter referred to for convenience as molten) state, and which then sets. To ensure that the casing is completely filled with the molten insulating material one or a number of spew-holes is provided. The flowing out of the insulating material through the spew-hole r spew-holes indicates that the metal casing is filled. The risk of moisture being drawn into the interior of the casing through a spew-hole when the apparatus is in service can be avoided by so shaping the spew-hole that the insulating material therein is formed with a head and a shank, the head being formed in an outer part of the spew-hole and the shank in an adjacent inner part of the spewhole. The outer part being of greater cross-sectional area than the inner part, a step i formed Within the spew-hole between the two parts. Shrinkage of the insulating material within the metal casing causes the head in the outer part of the spew-hole to be drawn tightly against the step to form a seal.

With the passage of time it may happen that the shank of insulating material within the spewhole stretches or flows to a small extent and as a result the insulating material may cease to make a tight or sufliciently tight fit with the step to give an adequate sealing efiect. An object of the present invention is to provide means for ensuring that even after a very considerable period of time, the seal will remain effective.

According to the present invention the spewhole is provided with a gasket which is made of a suitable resilient material and is squeezed between the step and the head of insulating material in the spew-hole due to the shrinkage of the insulating material within the metal casing. The gasket is held under compression between the head and the step and should there be some stretching or cold flowing of the material in the spew-hole with the passage of time, the gasket by changing its shape, is able to maintain pressure upon the step and the head of insulating material and thus compensate for any reduction of pressure at the seal caused by the stretching or cold flowing of the insulating material within the spew-hole. An efiective seal can thus be ensured over a considerable period of years.

Examples of suitable materials for the gasket are natural and synthetic rubbers.

Insulated Callenders Cables England, a British company Application June 7, 1950,

Serial No. 166,744

May 12, 1950 The invention will be described further with the aid of the accompanying drawings, wherein Figure 1 is a longitudinal view in elevation and partly in section of a cable-coupling member and,

Figure 2 is a fragmentary sectional elevation of the spew-hole drawn to a somewhat larger scale.

Referring first of all to Figure l, the coupling member is indicated generally by the reference numeral I. It is attached to one end of an electric cable 2 provided with conductors 3. The coupling member forms part of a coupling device of the plug and socket type and is shown provided with pins 4 for insertion into sockets carried by the other part of the coupling device, not shown.

Pins 4 are provided with terminal members 5 to which are attached in any convenient manner the conductors 3. The latter and the terminal members 5 are disposed within a metal casing 6, and are supported therein by insulating material The metal casing 6 is provided with a spewhole 8 which has an outer cylindrical portion 9 and an adjacent inner cylindrical portion I 0, the portion 9 being of greater cross-sectional area than the inner portion ID, the two portions thus forming between them an annular step II. The step slopes in a direction towards the interior of the casing 6 from its outer part towards its inner part. It will be seen from the figures that the shape of the spew-hole is such that when filled with molten insulating material which is allowed to set, the solid material will be so shaped that it has a head and a shank. The head is indicated by the reference numeral the reference numeral M.

The insulating material in a molten state is injected under pressure into the metal casing 6 in any suitable manner, the flowing out of the material through the spew-hole 8 indicating that the casing is full. Under these conditions there will, of course, be a body of insulating material within the metal casing and also a body of such material within the spew-hole, the one body being integral with the other.

Between the head l3 and the step H is interposed a rubber gasket [5. After the casing 6 and the spew-hole 8 have been filled with the insulating material 7, the latter sets and it also shrinks with the result that the head [3 is drawn into tight contact with the rubber gasket l5 forcing the latter against the step II to form a seal which will prevent the passage of moisture past it into the interior of the metal casing 6. The pres- I3 and the shank by sure exerted by the head upon the rubber gasket IE will cause it to change its shape and the pressure, preferably, is such that it is sufilcient to spread the gasket laterally by an amount sufiicient to force the gasket tightly against the surrounding wall of the spe -hole so as to increase the sealing efiect. If, after the course of some years, some small amount of stretching or cold flow of the insulating material forming the shank should have taken place, the resilience of the rubber gasket I is able to compensate for this since it is held under elastic compression. Should the pressure exerted upon it by the head become somewhat reduced, the gasket can change its shape and continue to exert sufficient pressure upon the head l3 and upon the step I l to maintain an efiective seal.

In Figure 1 the spew-hole 8 is shown in the course of being filled with the insulating material which is still molten and the level of which is continuing to rise within the spew-hole. In Figure 2 the filling process has been completed.

In Figure 1 there is shown a thin walled tube I6 disposed in the outer part of the spew-hole. This may be made of any suitable material, for example, brass, and is used to hold the rubber gasket down on to the step I l to prevent it being displaced by the rising of the molten insulating material in the spew-hole 8. The tube 16 may make a sliding or loose fit within the outer part of the spew-hole and its inner end bears upon the rubber gasket I5, with its outer end projecting a convenient distance beyond the outer end of the spew-hole so that pressure may be exerted upon the tube. After the filling operation has been completed, the tube It is withdrawn as indicated in Figure 2.

Where necessary, the wall of the metal casing 6 may be thickened up, as shown in Figures 1 and 2, to ensure an ample depth of the spew-hole.

From Figure 1 of the drawings it will be seen that the insulating material 1 within the metal casing 6 terminates at its inner end flush with the correspondingends of the terminal members 5 so as to leave a free space into which the pins 4 project and to provide for the entry of the latter into corresponding socket members of the other part of the coupling device. The metal casing 6 has at its end an externally threaded flange l2 whereby the other part of the coupling device may be attached to the coupling member 1.

It will be understood that the pins 4, or some of them, may be replaced by sockets, and that any number of pins and/or sockets may be used according to requirements. Futhermore, the metal casing 6 may be provided with one or morespewholes as may be required.

The invention is not limited thereto, but is particularly useful in those cases where a length of electric cable is required to be coupled to another length or to some other piece of electrical apparatus and polyethylene is used to support the pins and/or sockets of the coupling member and the ends of the cable conductors connected thereto, the molten polyethylene being forced under pressure into the interior of the metal casing and then being allowed to set.

What I claim as my invention is:

Electrical apparatus comprising a metal casing having a spew-hole, an outer part of which is of greater cross-sectional area than that of an adjacent inner part, a step being thus formed between the two parts, a mouldable insulating material in the casing, a head of insulating material in the outer part of the spew-hole and a shank of insulating material in the adjacent inner part thereof, a resilient gasket disposed between the head and the step held under elastic compression by the head and forming a sea1- against the entry of moisture through the spewhole into the casing, and a conducting member supported by the insulating material in the casing.

HENRY JOHNSON DIXON.

No references cited. 

